#COVID19 Serology (aka. #antibody) testing is a popular topic. Here is a tweetatorial on where things stand today in Ontario. As @UHN’s Deputy Division Head for Biochemistry, test validation and result interpretation are central to excellence in patient care. (1/12)

There is much hype about COVID-19 serology tests. It is important to know what the test tells you and what it does not tell you. For this to happen, tests need to be validated thoroughly in a clinical licensed laboratory before putting them to use.(2/12)

Some tests are poor quality: they don’t reliably detect antibody (not SENSITIVE) or even more concerning, they give positive results by cross-reacting to targets that are not related to COVID-19 (not SPECIFIC) (3/12)

If the # of overall infections in a population is low, then the test itself will perform less well in identifying infections accurately - even if it is a very sensitive and specific test. (4/12)

Our immune response to the virus will depend on case severity, age, genetic background and other co-morbidities such as whether you are an immune-compromised individual to begin with. These will impact sensitivity of any test.(5/12)

The tests measure total antibodies (Abs) present as one or more isotypes targeting different viral antigens. It does not tell you if the Ab neutralizes the virus; the latter is important for determining immunity status. (6/12)

Serology should NOT be used for diagnosis of acute COVID-19 infection; it does NOT predict protection from reinfection & should NOT be used to determine infectivity status. It currently CANNOT be used to issue “immunity passports”.(7/12)

Serology can identify a prior infection – even if that person has never showed symptoms (i.e. Asymptomatic). As such, the highest value of Ab testing currently is to deploy it at the population-level to aid in policy decision making (i.e. serosurveillance). (8/12)

Currently 4 serology tests have been approved by @GovCanHealth. Clinical lab licenses to perform serology testing to aid patient management decisions (at individual level) have NOT yet been issued by @ONTHealth.(9/12)

However, COVID-19 serology tests can be accessed for research use only from many clinical labs, and this research is CRITICAL to help inform accurate interpretation of serology results. (10/12)

Bottom line: Like all medical tests, serology testing is imperfect. But it’s one more tool, that when applied correctly (using the right assay; not a poor quality one), can help us better understand the epidemiology of the virus.(11/12)

With current data, it is too risky to use serology to inform how we act. The science will come, but until we know more – please wash your hands, physically distance and wear a mask when close to others, regardless of a serology result!(end)